Vulcan™ Black Stoneware (Extra Coarse) 164-VUX | Recommended Firing 1200-1260C / Cone 5-7
Recipe Adjustment: From batch number 2322 (week 23, 2022) onwards, recipe adjustments were made to the Vulcan recipe due to unavailability of a raw material. Fired results should be comparable with previously but as always testing is essential, particularly when glazing.
Vulcan Black Stoneware is unlike any other on the market, providing an unusual intense brown-black colour when fired in an oxidising atmosphere. In a reducing atmosphere, a metallic finish with shades of blue is obtained. Containing a very coarse grog (18-7 mesh) Vulcan Black Stoneware Coarse has been formulated especially for artistic ceramics. It behaves excellently during drying/firing and its high plasticity makes it ideal for modelling. It is widely used for murals and sculpture and is ideal for larger-scale handbuilding. Supplied in a 12.5kg bag.
Typical Data:
Firing range: 1200-1260ºC / Cone 5-7
Biscuit temperature: 1000ºC
Texture 9-10 on our indicative texture scale, smooth1, coarse 10.
Water content: 20%
Plasticity (IP Atterberg): 22
Carbonate content (CaCO3): 0%
Drying shrinkage: 6.5%
Firing shrinkage (1260ºC): 4.4%
Porosity (water absorption at 1260ºC): 7.8%
Dry bending strength: 3.0 N/mm2
Fired bending strength (1260ºC): 17.7 N/mm2
Thermal coefficient (25-500ºC): 51.3×10^-7ºC^-1
Technical Notes
Vulcan Black Stoneware (Extra Coarse) is not recommended for tableware due to the grog content. Please see Vulcan Black Stoneware (Fine) instead.
Vulcan is not toxic according to European Rules (CLP) and also American Rules (ASTM D 4236). The manganese dioxide content in Vulcan bodies is lower than 5%: Under the CLP regulation, the manganese dioxide content required for classification as toxic must be greater than 25%.
Use zinc-free (Zn-free) glazes to prevent unexpected reactions such as bubbling or colour changes. Other elements that can react are zirconium (Zr) and tin (Sn). We have found that Mayco zinc-free clear glaze is suitable for use with Vulcan bodies and does not seem to suffer from the usual problems caused by outgassing from the high oxide levels in black bodies. Many ^6 commercial glazes such as Mayco perform well on Vulcan but trial-and-error is needed. Also see our potclaysglazes Instagram feed/highlights.
Vulcan Black Stoneware is no longer recommended for use in casting slips due to the high plasticity which makes it difficult to correctly deflocculate.
